1. Field of the Invention
This invention relates to an apparatus for mixing and dispersing a fluid such as liquid, powder, or mixture thereof in a container. More particularly, this invention relates to an apparatus for mixing and dispersing a fluid such as liquid, powder, or mixture thereof in a container, such as a tank or a mixing tank incorporated in a production line by vibrating vibration vanes in the container.
2. Description of the Related Art
Heretofore, agitational mixers have been used for the manufacture of various chemical products, such as cosmetic articles, foodstuffs, medicines and drugs, coating materials, and inks and for the agitational mixture of materials for surface treatment.
The agitational mixers include those utilizing the rotation of stirring vanes, those having a stirring shaft coincident with the central axis of a container for the fluid under treatment, those having a stirring shaft inclined relative to the central axis of the container, and those having a stirring shaft disposed on a lateral wall of the container, for example. Some of the agitational mixers are provided with means for moving the container itself, as by imparting rotation to a cylindrical container. Part of the agitational mixers use such means as pumps, nozzles, and orifices for fluidifying a liquid. Some other agitational mixers are adapted to blow air in the tank as through a nozzle formed in the bottom part of the tank.
Among other agitational mixers, the stirrers which are operated by the rotation of rotary stirring vanes are used prevalently on the commercial basis.
The stirrers provided with rotary vanes, however, have various drawbacks as discussed below. The mixture emanating from such a stirrer, therefore, must be dispersed by additional use of a dispersing device, such as a roll mill, a sand grinder, or a colloid mill.
(1) The conventional stirrer provided with rotary vanes, when desired to mix a liquid homogeneously with a fine powder insoluble in the liquid, is at a disadvantage in allowing the produced mixture to separate quickly into the powder and the liquid after the stirring is stopped.
(2) This stirrer has the disadvantage that since the stirring is not easily effected in the bottom part of a container, the fine powder is not completely dispersed but is allowed to sediment in the bottom part.
(3) The stirrer sustains the resistance of an initial load necessary for rotational flow of the entire liquid and requires extra electric power during the initial stage of its operation.
In this case, the stirrer is enabled to produce a stirring motion with uniform electric power by gradually introducing the liquid to the site of agitation. This gradual addition of the liquid consumes time and labor to a very great extent.
(4) This stirrer tends to generate a whirlpool in the central part thereof and engulf air in the whirlpool and, as a result, impart a chemical influence to the liquid being stirred.
(5) The stirrer, when used for mixing two species of powder, fails to effect homogeneous mixture.
(6) Generally, owing to the load which is exerted upon the site of stirring, this stirrer can generate idle rotation when the part of the stirring vanes immersed in the liquid is small. Thus, the operation of this stirrer requires a constant test of such factors as amount of the liquid under treatment.
(7) As respects the number of revolutions per unit time, the stirrer generally encounters difficulty in producing a rotation at a high rate and, more often than not, generates only slow stirring. Since the stirrer is typically capable of about 300 revolutions per minute, it calls for a long time for producing desired stirring.
When the stirrer is used for dispersing an insoluble powder in a liquid, therefore, the time required for thorough mixture is further elongated.
(8) When the contents of a relatively large tank are required to be homogeneously stirred, it becomes necessary to use simultaneously several stirrers provided with rotary vanes and arranged efficiently.
(9) When the container to be used happens to have a circular cross section, it must be provided on the inner wall thereof with special means for inhibiting rotation of the contents thereof such as, for example, a baffle plate.